Discussion about the Korg PolySix synthesizer

After the repair from a batteryleak, I found out that some of the oscillators are not completely in the same frequentie.

I have the equipment, but do not completely understand the calibration procedure. So I have some (maybe stupid) questions and hope that someone can help me to make this old Polysix sounding like a nightingale again :-)

The manual, page 20, say's:
-- Change cirquitboard slide switch to opposite position. (Away from VR1) --
Does this mean up or down, because in my PS VR1 is left from the switch. Maybe they mean from the letters VR1?

-- Play C6 and adjust VR11 to 0 cent --
Compared to what must it be 0 cent.
I miss probibly where to connect my scope.

Anyone can put me in the right direction?

> -- Change cirquitboard slide switch to opposite position. (Away from VR1) --
> Does this mean up or down, because in my PS VR1 is left from the switch.
>Maybe
> they mean from the letters VR1?

Substitute "CN12" for "VR1" and things should be clearer. The regular
tuning is done with the switch AWAY from the connector.

> -- Play C6 and adjust VR11 to 0 cent --
> Compared to what must it be 0 cent.

Well, to C of course. Just connect a regular (electronic) tuner to the
output of the Polysix and observe it. Alternatively you can connect your
scope to the "SIG OUT" test point (TP1).

>Substitute "CN12" for "VR1" and things should be clearer. The regular
>tuning is done with the switch AWAY from the connector.

That would be UP in my case then.
What does this switch actualy do?
I see a change in freq when I switch up or down.

>> -- Play C6 and adjust VR11 to 0 cent --
>> Compared to what must it be 0 cent.

>Well, to C of course. Just connect a regular (electronic) tuner to >the output of the Polysix and observe it. Alternatively you can
>connect your scope to the "SIG OUT" test point (TP1).

I'll put then a reference signal of 440 Hz on my A-channel of the scope and the the B-channel will be connected to TP1 then.
The Polysix is warming up now, and later I'll try to calibrate again.

I will post the result.

> What does this switch actualy do?
> I see a change in freq when I switch up or down.

It puts the Polysix into "stretched tuning". By doing this the  higher
notes are tuned slightly sharp; read: the octaves are no longer perfect.
Stretched tuning comes originally from the piano and (as far as I know) has
something to do with the inharmonicities of the piano strings (some
harmonics tend to go out of tune).
The tuning procedure is done in "regular tuning". If you hold down a high
note and move the switch you'll notice that the pitch goes very slightly up
or down. If the pitch is higher you're in stretched tuning.

> I'll put then a reference signal of 440 Hz on my A-channel of the scope and
> the the B-channel will be connected to TP1 then.

This probably won't help much when you try to tune C6. I suggest using a
tuner. There are some free software tuners to be found although I can't say
anything about their quality (I'm using a hardware tuner myself).

> > I'll put then a reference signal of 440 Hz on my A-channel of the scope and
> > the the B-channel will be connected to TP1 then.
> This probably won't help much when you try to tune C6. I suggest using a
> tuner. There are some free software tuners to be found although I can't say
> anything about their quality (I'm using a hardware tuner myself).

You're completely right, I mixed up de freq's.

But I think I got the picture now.
I found a software tuner, and connected the Polysix to the computer, and tuned the oscillators.
It's much more accurate then with the scope I found out.
All but 1 oscillator is in 0,2 cent now.
That one oscillator could not be tuned high enough, because the pot was at max or min. So I think I'll have to check out the other parts in that oscillator.

Learned a lot again this evening :-)
In a few day's I can continue.

Today finished the calibrating procedure, and everything was clear.
The only little confusing part was that there was a reference to the VR1 on the KLM-396, because I had the new production board, I couldn't find it offcourse :-)
Guessed it must be VR15 then.

But afterall I got all oscillators in 0,2 cent.
Even the oscillator wich couldn't tune enough before , because I now raised the whole deviation with VR3.

The synth sounds like a charm again, thanks for info and helping :-)

> But I think I got the picture now.
> I found a software tuner, and connected the Polysix to the computer, and tuned the oscillators.
> It's much more accurate then with the scope I found out.
> All but 1 oscillator is in 0,2 cent now.
> That one oscillator could not be tuned high enough, because the pot was at max or min. So I think I'll have to check out the other parts in that oscillator.

A few day's later now.

After I played a bit more with the synth, I think the calibration stil can be improved.
Sometimes key's pressed at the same time, give some dis-resonance, but maybe that is the charm of a real analogic synth ;-)

I want to change the VR10, VR11 an VR15 for a precision trimpots, like these:
http://cgi.ebay.nl/10-x-100K-ohm-Precision-3296-Variable-Resistor-Trim-Pot-/300452503889?pt=LH_DefaultDomain_0&hash=item45f45d6151

From the schematic's of board KLM-366 (new production) they must have the following specs:
VR10 - 100k
VR11 - 2k2
VR15 - 4k7

The schema'tics are a little blury(?) so I'm not quite sure, if I read them correct.

Also I read about replacing the elco's on the oscillator board.
Would that be wise, to do in the same time? They look stil good.
And I guess they only ment the elco's in the oscillator part?

And a final question (at least for now) about the stretched tuning.
I got answer on what it is, but do I understand correct, that when tuning the synth this switch has to be in normal position?
The SM say's to switch it on, when tuning.
I'm a little bit confused in this.
When to use this stretched tuning then?

Als I found out that the longer the synth is turned on, the nicer he sounds.

(Before I start tuning, I leaf it on, for at least 1 hour)

--- In PolySix@yahoogroups.com, "sigma.draconis" <mreuvekamp@...> wrote:

>
> 
> 
> 
> Today finished the calibrating procedure, and everything was clear.
> The only little confusing part was that there was a reference to the VR1 on the KLM-396, because I had the new production board, I couldn't find it offcourse :-)
> Guessed it must be VR15 then.
> 
> But afterall I got all oscillators in 0,2 cent.
> Even the oscillator wich couldn't tune enough before , because I now raised the whole deviation with VR3.
> 
> The synth sounds like a charm again, thanks for info and helping :-)
>